Pen



FIG. 1 shows a front-right side perspective view of my design for a pen;

FIG. 2 shows a right side view thereof;

FIG. 3 shows a rear view thereof;

FIG. 4 shows a top view thereof;

FIG. 5 shows a left side view thereof;

FIG. 6 shows a front view thereof;

FIG. 7 shows a bottom view thereof; and,

FIG. 8 shows a front perspective view thereof. 

The ornamental design for a pen, as shown and described. 